1. Field of the Invention
The present invention relates to a micro-droplet generator, particularly to a micro-droplet generator for spraying gasoline, machine oil, essence or other fluids from a chamber, wherein negative pressure is maintained in the chamber to avoid leaking due to gravitation, and a spraying plate with a microstructure is used, having gradually narrowing holes and gradually widening holes for completely removing drops from the spray plate if spraying force is not sufficient.
2. Description of Related Art
A micro-droplet generator needs to maintain a negative pressure to avoid leaking due to gravitation. To prevent a reduction in the rate of sprayed fluid because of too large negative pressure, automatic regulation of the negative pressure is required. Furthermore, if spraying force is insufficient, remaining liquid will accumulate on spraying plate, blocking normal exchange of liquid and air through holes, so that continuous spraying is hampered.
U.S. Pat. No. 6,116,517 “Droplet mist generator”, as shown in FIGS. 4–6, discloses a droplet generator having a chamber 1 which is via two tubes connected with a storage tank (not shown), a piezoelectric plate 2, and a plurality of spraying holes 3. The characteristics of the droplet generator are as follows. (1) The piezoelectric plate 2 is horizontally placed inside the chamber 1, performing a vibrating movement driving droplets out of the spraying holes 3 on one side of the piezoelectric plate 2. (2) The spraying holes 3 are oriented parallel to the vibrating movement of the piezoelectric plate 2. (3) The spraying holes 3 are oriented perpendicular to the vibrating movement of the piezoelectric plate 2 (not shown) . The vertical vibrating movement of the piezoelectric plate 2 drives droplets simultaneously and on a common side out of the spraying holes 3.
For simultaneous refilling of fluid and removing of air bubbles, restrictions in the directions of spraying and a refilling system are required. Furthermore, control of negative pressure is not mentioned in the cited patent, so that the following shortcomings result: (1) Due to gravitation, liquid sticks to the spraying surface, blocking spraying of droplets, thus hampering continuous spraying of droplets. (2) Refilling of fluid and removing of air bubbles depends on the effect of gravitation and hydrostatic pressure, restricting directions of spraying.